Semiconductor components are typically formed jointly on a wafer-type semiconductor substrate having a stable thickness. The semiconductor wafer is furthermore thinned and severed in predefined separating regions, as a result of which individual components are present. For components having both front-side and rear-side contacts, for example, luminescence diode chips, a metal-semiconductor contact is formed at a rear side of the semiconductor wafer after thinning.
For singulation it is possible to carry out sawing or separation by grinding, or laser cutting. However, such separating processes can lead to crystal damage, which is associated with a risk of breaking in the case of relatively thin components or chips. In order to avoid this and in order to produce chips that are more stable, provision can be made for etching separating trenches. In this regard, anisotropic dry etching processes afford sufficiently high etching rates on semiconductor materials. What is problematic however, is the severing of metallic layers, for which dry or plasma etching is unsuitable.
One possible approach consists in processing a semiconductor substrate as usual, preparing the front side in the separating regions to be free of metal, thinning the substrate, providing the rear side with a metal-semiconductor contact (and possible further layers), and mounting with the rear side onto a film. Afterward, separating trenches can be produced from the front side in an anisotropic etching process, wherein the trench etching can stop on the metallic contact layer at the rear side. The singulation can be completed by carrying out wet-chemical etching of the rear-side metal or tearing the latter by expanding the film. However, this results in an unstable manufacturing process.
Alternatively, provision can be made for photolithographically patterning the metal layer before the separating trenches are etched. However, this requires complex front to rear side alignment and, owing to the presence of the thin semiconductor substrate, can result in the latter breaking. In order to avoid this, consideration can be given to connecting the semiconductor substrate to a stabilizing auxiliary substrate. This approach increases the outlay, and can likewise lead to losses of yield when the auxiliary substrate is removed.